1. Field of the Invention
The present invention relates to a fluid pump including a motor for rotationally driving an impeller, a cooling apparatus including such a fluid pump, and to an electrical appliance including such a cooling apparatus.
2. Description of the Related Art
A fluid pump is known which includes a motor having a rotor to which an impeller is integrally fixed for rotation together with the rotor, so that the pump vanes of the impeller serve to suction a fluid into a pump chamber via a suction port, and to discharge the fluid out of the pump chamber via a discharge port, as disclosed in Japanese Published Unexamined Patent Application No. 2001-123978 and Japanese Published Unexamined Patent Application No. 2001-132677, for example.
It has been proposed to incorporate this type of a fluid pump in an electrical appliance such as a personal computer, for cooling a CPU, which is a heat-generating component. In this case, the configuration may be as follows. A face of the pump case is disposed in contact with the CPU, and an impeller in the fluid pump is rotated to cause a cooling fluid (liquid) to circulate inside the pump, so as to absorb heat generated by the CPU via the pump case into the fluid flowing in the pump, thus to cool the CPU.
However, an existing fluid pump has a drawback that relatively strong vibration is generated during the pump operation (during the motor rotation), accompanied with a significant noise. A reason can be described as follows, for example.
The case of the fluid pump is provided with a pressure generating protrusion located inside the pump chamber between a suction port and a discharge port, so as to confront the pump vanes of the impeller. When the motor rotates the impeller for operating the pump, the fluid pressed by the pump vanes of the impeller collides with the pressure generating protrusion, which generates considerable vibration. In addition, when the vibration due to the collision of the fluid with the pressure generating protrusion (vibration due to pressure generation) and vibration due to cogging torque of the motor rotating the impeller are generated at the same timing, the vibration may be augmented.
In particular, when such a fluid pump is employed in an electrical appliance, for example, for cooling a CPU in a personal computer, the vibration and noise are critical issues to be overcome.